This section provides background information related to the present disclosure which is not necessarily prior art.
Various casting processes for forming articles can use dies having a mold cavity with cavity inserts that can include one or more core elements. The mold cavity can be formed of outer molds and inner core elements each having features and reliefs that form details, recesses, and cavities in a casting when molten material such as liquid metal is poured or forced into the mold. For example, casting processes can be used to form engine blocks and transmission housings from molten aluminum alloys for use in internal combustion engines and transmissions for vehicles and other applications. Inner core elements can be constructed from bonded sand where the inner core elements can be extracted from the casting subsequent to the forming process.
Portions of a cast article can be subject to high-stress in use, and it can be desirable to impart varying metallurgical properties to such portions. For example, a time-rate removal of thermal energy from liquid metal during casting can affect grain structure. Increased cooling and solidification of the poured liquid metal can lead to an improvement, in some cases, of material properties such as tensile strength, fatigue strength, and machinability. To this end, casting processes can use heat transfer devices in proximity to specific portions of a casting in place of or in conjunction with features on the mold and core elements. For example, heat transfer devices can be used to control the cooling rate at bulkheads and crankshaft bearing surfaces on cast engine blocks.
Heat transfer devices for controlling the cooling rate of cast articles can include devices that circulate a coolant such as water through one or more portions of a die casting assembly. However, leakage of die cooling water can cause quality issues with the cast article. Die cooling water leaks can also be difficult to detect and locate. Leaks can occur in various parts of a die casting assembly, including valves, tubes, pipes, fittings, and/or die cracks. In some instances, a leak can start after the die has run several shots or the leak may not occur until the die is hot and/or stressed during lock-up. Since leaks can be hard to find and can present quality issues, multiple castings failing to meet desired specifications can be made before the leak is identified and fixed. Moreover, where the casting process employs vacuum, the vacuum can exacerbate the leak as it can pull leaking coolant into the die cavity.
Checking for leaks can include pressure checking the die in the tool room prior to set-up. Leaks can be visually checked by inspecting for coolant. For example, the die is heated in the die casting assembly, the die is closed, water and vacuum are turned on, and the die is then manually opened and inspected for leaks. Post-casting inspection can also reveal signs of leaks which can manifest as dark stains on a casting. However, such methods are labor intensive and remove the die casting assembly from fabrication, reducing production times and increasing costs.